Check all the wires at the throttle body connector for broken inside the insulation. Common problem. You'll have to cut the tape off the wires and peel back the black plastic conduit. Pull test each wire from the connector to about four inches back. Look for one of the wires to stretch and the color of the insulation to turn wihite. This is where the copper inside is broken. Also check each wire at the terminal for poor crimp or broken right at the crimp. Also check the black with white stripe PCM ground wire from the large wiring harness at the back passenger side of the intake manifold down to where it bolts to the block between the intake and the wirewall. Pull on it pretty good to make sure it's not broken. This is the most commonly rodent chewed wire on these trucks. In rare cases the bolt holding it down is loose. If you still don't find anything, have the battery load tested. When the battery is a little weak it can still start the truck but the TACM and the PCM "wake up" at different times and do not communicate causing REP.